This invention relates to a mobile telephone system in which a mobile telephone apparatus comprises not only a radio section mainly serving as a mobile telephone set adapted to carry out radio communication but also a GPS unit adapted to receive GPS (Global Positioning System) information so that position data of the mobile telephone apparatus itself is acquired by information processing of the GPS information and reported, via radio communication to a mobile telephone base station, to a telephone network connected to the base station and, in particular, to a mobile telephone system which has a backup function in case where the mobile telephone apparatus is used in an environment such that the GPS unit thereof can not appropriately receive the GPS information and which achieves low power consumption and saving of a memory capacity in the mobile telephone apparatus.
Recently, in the field of mobile telephone communication, it is considered to use in a mobile telephone system a GPS unit capable of receiving GPS information transmitted from a GPS satellite and including time information, position information, and map information. This arises from a demand for applications in case where a user of a mobile telephone apparatus sends an emergency report via radio communication and another party involved in communication desires to identify a user's position or in case where another party searches the position of a possessor of a mobile telephone apparatus. In addition, there is also a demand for an application such that a user of a mobile telephone apparatus desires to acquire map information of his neighborhood for the sake of convenience.
As a known technique using the GPS unit in the field of mobile telephone communication, proposals have been made of a structure in which a mobile telephone base station comprises a GPS unit as in a radio telephone controller with GPS disclosed in Japanese Unexamined Patent Publication (JP-A) No. H06-213998, and another structure in which a mobile telephone apparatus comprises a, GPS unit as in a mobile telephone set with a GPS receiver disclosed in Japanese Unexamined Patent Publication (JP-A) No. H09-98475 and a mobile telephone with a GPS unit disclosed in Japanese Unexamined Patent Publication (JP-A) No. H11-18159.
Generally, a mobile telephone apparatus containing a GPS unit is not always used in a place where the GPS information from the GPS satellite can be received in a good condition but is often used in an unreceivable place, typically, an underground mall. In addition, in an automobile where the mobile telephone apparatus is frequently used, the GPS information is often impossible to receive. In order to effectively utilize the GPS information in such cases, the underground mall or a tunnel is provided with a GPS communication mobile telephone base station which covers a local region as a communication area. In the automobile, a GPS unit used as car navigation is mounted. In this manner, in case where the GPS information is difficult to be directly used by the GPS unit contained in the mobile telephone apparatus, the GPS information obtained by the GPS communication mobile telephone base station or the GPS unit mounted in the automobile is used instead.
As other known techniques related to data communication, including the GPS information, applicable to the mobile telephone apparatus, proposals have been made of a mobile information apparatus and a communication IC card used in the information apparatus disclosed in Japanese Unexamined Patent Publication (JP-A) No. H08-153075, a position information service system disclosed in Japanese Unexamined Patent Publication (JP-A) No. H09-68566, a method of providing information to a mobile terminal, an information providing system, and a mobile terminal disclosed in Japanese Unexamined Patent Publication (JP-A) No. H09-130861, a mobile object position detecting apparatus disclosed in Japanese Unexamined Patent Publication (JP-A) No. H09-281212, a mobile radio communication terminal position display apparatus disclosed in Japanese Unexamined Patent Publication (JP-A) No. H10-79971, and a data communication method, a mobile data communication apparatus, and a recording medium disclosed in Japanese Unexamined Patent Publication (JP-A) No. H11-113066.
In the mobile telephone system utilizing the GPS unit described above, countermeasures are taken to prepare for the circumstance where the GPS unit contained in the mobile telephone apparatus can not directly receive the GPS information in a good condition. Specifically, the GPS communication mobile telephone base station is arranged at the place where the reception of the GPS information is difficult. Alternatively, in case of the automobile, the GPS unit used as the car navigation is mounted. Thus, the GPS information obtained by the GPS communication mobile telephone base station or the GPS unit mounted in the automobile is used as a substitute. Nevertheless, if the reception state of the GPS information by the GPS unit contained in the mobile telephone apparatus is inferior, it is difficult to effectively utilize the GPS information.
Furthermore, in the mobile telephone apparatus containing the GPS unit, a large current consumption is required upon using the GPS unit as compared with a current consumption in a standby state of the mobile telephone apparatus itself. Therefore, it is difficult for the mobile telephone apparatus energized by an ordinary battery to desiredly use the GPS unit requiring a large power consumption. As a result, the GPS unit can not effectively be utilized.
Furthermore, in the mobile telephone apparatus provided with the GPS unit, a memory medium such as a semiconductor memory capable of memorizing an enormously large quantity of information is required in order to use map information contained in the GPS information directly obtained by the GPS unit contained therein. For example, in case where a CD-ROM or a DVD-ROM having a large memory capacity is used and utilized like in the car navigation, no problem will arise. However, in case where the map information is used only by the GPS unit contained in the mobile telephone apparatus, a special memory medium having a large memory capacity is required so that the reduction in size and weight required for the mobile telephone apparatus can not be assured and the increase in cost is inevitable. Thus, at present, it is not easy to obtain and use the map information by the GPS unit contained in the mobile telephone apparatus.
In addition, the mobile telephone apparatus is typically provided with a clock section indicative of a current time instant. However, the time instant in the clock section is much less accurate than the time instant information given by a frequency of a quartz oscillator and contained in the GPS information transmitted from the GPS satellite. Thus, the clock section presently used can not indicate an accurate time instant.